JPS6364647A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent the disturbance of a tracking error signal in an ID part and to permit exact tracking control by setting the optical depth direction of the ID pit part and the guide groove for tracking control at the relative direction with respect to a disk reference plane. CONSTITUTION:Pits 10 of the ID part D are formed as projecting parts which project upward from the reference plane K of an optical disk LD. The optical depth direction of the pits 10 are set at the opposite direction with respect to the guide grooves E formed as recesses at lambda/8n with the reference plane K of the disk LD. The projecting height of the pits 10 is set at lambda/4n with respect to the reference plane K. The disturbance of the tracking error signal in the ID part D is thereby prevented with the simple structure and the exact tracking control is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical disc, and more specifically, an ID part in which an address signal and a synchronization signal are recorded is followed by a data part in which information content is recorded, and the ID part and the data part are separated. The present invention relates to an optical disc having guide grooves for tracking control formed on both sides.

(Prior Art) As is well known, an optical disc is one type of information recording medium.

In this optical disk, as shown in FIG. 3, eight information recording layers B made of, for example, an amorphous magnetic film are formed on a transparent substrate A such as PMMA. Information is written to the recording layer B or information is read from pits formed in the recording layer B by irradiating laser light focused to about 1 μm.

By the way, in such an optical disc, as shown in the third diagram, there is an ID section consisting of a data section C in which information contents are recorded and a pre-group in which address signals and synchronization signals for this data section are recorded. Tracking guide grooves E are provided on both sides of each part to accurately position the laser beam irradiation position with respect to each part.

An optical system shown in FIG. 4 is used to scan the above-mentioned optical disk by laser beam irradiation.

That is, this optical system has a general structure used for scanning this lightning disk, and the laser beam irradiated from the laser source 1 is coupled and
The parallel light is made into parallel light by the lens 2, and is spot irradiated onto the optical disc LD via the polarizing beam splitter 3.1/4λ plate 4 and the objective lens 5. On the other hand, optical disc L
The reflected and diffracted light from D passes through the polarizing beam splinter 3 via the objective lens S, enters the light receiving element 6 consisting of a two-split photodiode, enters the light receiving element 6, and is tracked in the light receiving element 6. It is photoelectrically converted to determine the control signal.

It is well known that in such an optical disc, the amount of reflected light and the characteristics with respect to the track signal, that is, the tracking error signal, have a correlation with the depth of the guide groove.

That is, as shown in FIG. 5, if λ is the wavelength of the laser beam and n is the refractive index of the transparent substrate of the optical disk, then
It is known that the tracking error signal reaches its maximum at λ/8n, and the decrease in the amount of reflected light reaches its maximum at λ/4n. Specifically, as shown in FIG. 7, the depth of the guide groove E is λ/8p, and the depth of the pit G is λ/4n.
(For example, the signal from the
50733).

However, the pits in the ID section are λ as described above.
/4n depth creates an ideal condition with almost no signal disturbance, but in reality, as shown in Figure 6 (B), the shape of the groove created by laser beam irradiation is similar to that in Figure 6 (A). It is not rectangular, but often has a parabolic cross section.

Therefore, in pits having such a shape, as shown in FIG. 7, an erroneous signal corresponding to a tracking error signal is obtained even from the pit portion.

That is, in the case of a conventional optical disc, as shown in FIG. 7(B)
As shown in the figure, since the phase depths of both the pits near the ID portion and the guide groove E are set in the same direction, the track signal when such an optical disc is irradiated with laser light will be As shown in FIG. 7(A).

However, as is clear from FIG. 7(A), even when the pit depth difference in the ID part is set as λ/4n, as shown in FIG.
If the actual shape of the pit is parabolic as shown in B), a signal having the same shape as the tracking error signal that is out of phase by πrad with respect to the tracking error signal from the guide groove will also be generated from the pit in the ID section. Occur.

Therefore, the tracking error signal includes signals from the pits of the ID section in addition to the signals from the guide groove, and as a result, the tracking error signal cannot be accurately obtained and accurate tracking control cannot be performed. It disappears.

(Objective) In view of the problems of conventional optical discs, an object of the present invention is to obtain an optical disc from which only the tracking error signal obtained from the guide groove can be extracted.

(Structure) In order to achieve this object, the present invention provides guide grooves for tracking control on both sides of a recording band having a hit area and a data area continuous thereto, and optically controls the pits and guide grooves. This is characterized in that the depth direction is set relative to the disk reference surface.

Embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2 below.

FIG. 1 is a perspective view corresponding to FIG. 3, in which the same components as those in FIG. 3 are designated by the same reference numerals.

The feature of this embodiment is that the optical depth direction of the ID pit portion is set in the opposite direction to the optical depth direction of the guide groove.

That is, the pits 10 in the ID portion are formed by protrusions that protrude upward with respect to the reference surface K of the optical disc LD. The pit 1° is set so that its optical depth direction is opposite to the guide groove E formed in the concave portion at an angle of λ/8n with respect to the reference axis K of the optical disc LD.

Note that the protrusion height of the pit 10 is λ/ with respect to the reference plane K.
The setting of 4n is similar to the conventional pit.

Since this embodiment has the above structure, the structure shown in FIG. 2(B)
As shown in , when laser beam irradiation is performed, the progress of the reflected light from the 10 ID pits is corrected by the protruding height of the pit, with respect to the tracking signal caused by the reflected light from the guide groove E. As a result, as shown in FIG. 2(A), a tracking error signal from the pit portion is obtained with no phase shift.

In other words, the reflected light from the guide groove and the tracking error signal from the conventional pit will be out of phase by the amount corresponding to the depth because the depth direction of the pit and the guide groove is the same. In this embodiment, it is possible to correct and eliminate the phase shift of the tracking error signal due to the reflected light from the guide groove and the reflected light from the pit.

Therefore, the signal from the pit is included in the tracking error signal from the guide groove, and no signal disturbance occurs between the two.

(Effects) As is clear from the above explanation, according to the present invention, the optical depth direction of the pit in the ID portion is set in the opposite direction with respect to the same direction of the guide groove across the reference surface of the optical disc. The simple structure prevents the tracking error signal from being disturbed in the ID section and enables accurate tracking control.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of an optical disc according to the present invention, FIG. 2 (A) is a diagram showing the operation of an embodiment of the present invention, and FIG. 2 (B)
3 is a sectional view of an optical disc showing the main part of an embodiment of the present invention.
FIG. 4 is an explanatory diagram of an optical scanning device used in an embodiment of the present invention, and FIG. 5 is a diagram showing the depths of guide grooves and pits, the amount of reflected light, and the amount of reflected light in a conventional optical disc. A diagram for explaining the correlation with a tracking error signal, FIG. 6 is a cross-sectional view of a part of a conventional optical disc, and FIG. , Figure 7 (
B) is a sectional view of the optical disc from which FIG. 7(A) is obtained. 10...Pit, LD...Optical disk, D...I
D section, E...guide groove. 1i Poisoning ==) 1 Written amendment to the proceedings October 13, 1985 1. Indication of the case 1988 Patent Application No. 209810 2. Name of the invention Optical disk 3. Person making the amendment Relationship to the case Patent application Person Name (674) Ricoh Co., Ltd. 4, Agent
Person 5, "Detailed Description of the Invention" column of the specification to be amended (1) Change "equity" in line 4 of page 4 of the specification to "unexamined patent application". (2) "As much as the depth corresponds to" in page 7, line 14.
changed to "Due to the positional relationship between the IO pit located in the center and the guide grooves located at both ends."

Claims (1)

[Claims] In an optical disc in which guide grooves for tracking control are formed on both sides of a recording band having an ID pit area in which an address signal, etc. for recorded information is recorded and a data pit area continuous thereto, the pit area and the guide groove are An optical disc characterized in that an optical depth direction is set relative to a disc reference surface.